Fibrous articles having improved water resistance



United States Patent 3,405,004 FIBROUS ARTICLES HAVING IMPROVED WATER RESISTANCE Richard H. Hall, Andrew J. Sikkema, and Charles G.

Humiston, Midland, William A. Foster, Mapleton, and Junior J. Lamson, Bay City, Mich, assignors to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Filed Nov. 25, 1964, Ser. No. 413,982

4 Claims. (Cl. 117-155) ABSTRACT OF THE DISCLOSURE A process which comprises distributing throughout a fibrous material an aqueous dispersion of a copolymer of a tertiary alkylstyrene such as te-rtiary-butylstyrene and a conjugated diolefin such as isoprene and drying the resulting composition. The aqueous dispersion is distributed throughout the fibrous material by any of a variety of methods such as -'by adding the dispersion to a' slurry of the fibers (which is then passed onto suitable sheeting equipment) or by applying the dispersion to webs or mats of the fibrous material by roll coating or spraying or by running the webs through vats of the aqueous dispersion. Fibrous products and articles having improved water repellancy are obtained.

This invention is directed to a method of increasing the water resistance of fibrous materials such as paper, textiles, leather and the like, and in particular to a new sizing ingredient and a process for its use.

It is known that the deposition of certain resins on fibrous materials such as paper and the like will significantly enhance the water resistance of the material. Although the presently available water resistant fibrous materials constitute a major technical advance, the art continues to seek materials having still greater Water resistance.

In accordance with the present invention fibrous materials such as paper and textile products having improved resistance to water penetration are prepared by contacting fibrous product with a copolymer of a conjugated aliphatic diene and a tertiary alkylsty'rene having the structural formula wherein R is a tertiary alkyl group containing 4 to 20 carbon atoms.

The copolymers used in the process of the present invention are formed from about to about 90 percent by weight of the tertiary alkylstyrene and from about 10 to about 90 percent by weight of the conjugated aliphatic diolefin; preferably, the copolymer contains from about 25 to about 85 percent by weight of the tertiary alkylstyrene and from about to about 75 percent by weight of the conjugated aliphatic diolefin.

Illustrative examples of tertiary alkylstyrenes. which may be used to prepare the copolymers include paraand meta-tertiary butylstyrene and mixtures thereof, tertiary amylstyrene, tertiary hexylstyrene, tertiary octylstyrene, tertiary dodecylstyrene, tertiary heptadecylstyrene and tertiary eicosylstyrene.

Typical examples of conjugated aliphatic dienes which may be used to prepare the copolymers include 1,3-

ice

butadiene (usually referred to simply as butadiene), isoprene, 2,3-dimethyl-1,3-butadiene, piperylene, chloroprene, 2,3-dichloro-1,3-butadiene and cyclopentadiene.

The copolymers useful in the process of the present invention may be prepared by subjecting the monomers to the polymerization methods conventionally used with free radical catalyzed aqueous systems, i.e., emulsion-, and solution polymerization in the presence of actinic light, ultra-violet irradiation, gamma radiation, azo oatalyst and peroxides.

The tertiary alkylstyrene/conjugated diolefin copolyme-rs are conveniently applied to the fibrous material as an aqueous dispersion or latex.

The aqueous dispersion of the tertiary alkylstyrene copolymer can be prepared by aqueous emulsion polymerization of the corresponding monomers or by post dispersing the preformed copolymer, preferably by emulsion polymerization as it is the most convenient and economical procedure. As a general rule, the amount of copolymer solids in the aqueous dispersion ranges from about 2-0 to about 50 percent and preferably about 30 to about 40 percent by weight of the dispersion. The dispersion may be diluted to reduce the solids content prior to treatment of the fibrous material. The aqueous dispersion of the copolymer also ordinarily includes a surfactant in addition to the aqueous dispersed colloidal particles of the polymer for the purpose of stabilizing the dispersion. The concentration of surfactant can be the usual proportion of 0.5 to 10 percent based on the weight of the copolymer. The surfactant, preferably water soluble, can be non-ionic, anionic or cationic.

The aqueous dispersion of copolymer can be applied to the surface of the fibrous material such as paper or textile by any of a variety of conventional methods which will distribute the copolymer substantially uniformly throughout the fibrous material as for example running the materials through vats of the aqueous dispersion, roll coating or spraying. After the aqueous dispersion of the copolymer is applied to the surface of the article, the article is dried usually at a temperature of to C. for a time suflicient to effect removal of the aqueous carrier; lower drying temperatures may be employed, but at these lower temperatures, the time necessary for drying may be impracticable for commercial purposes.

In case of paper articles an alternative method for treating the paper with the copolymer may be effected by incorporating the copolymer in the paper stock prior to the formation of sheets therefrom. Thus an aqueous dispersion of the tertiary alkylstyrene/ conjugated aliphatic diolefin copolymer may be added to an aqueous slurry of the paper pulp and most conveniently the aqueous dispersion of the copolymer may be introduced into the pulp slurry at any point prior to formation of the web, preferably after the beating cycle.

After adding the copolymer additament to the pulp slurry the treated and suitably refined aqueous fiber slurry is passed onto any suitable sheeting equipment whereupon the fibrous suspended solids are felted from the aqueous dispersing medium in the form of a web-like sheet. Usually, these operations are continuous in nature and maybe accomplished with such machines as the Fourdrinier paper machine and the like. The wet felted web may then be subjected to drying prior to calendering and/or coating and/or other finishing operations.

The exact amount of copolymer used to treat the fibrous material may vary depending on the nature of the base article to which the copolymer is to be applied, the means of application of the copolymer and the degree of water repellency desired. In general, from about 0.05 to about 3 percent by weight of the copolymer based on the weight of the article to be treated is employed. Higher amounts of up to about 25 percent of the copolymer may be required for special papers or textiles or circumstances.

To illustrate the manner in which the invention may be carried out, the following examples are given. It is to be understood, however, that the examples are for the purpose of illustration and the invention is not to be regarded as limited to any of the specific materials or conditions recited therein. Unless otherwise stated, all percentages cited in the examples below are based on weight.

Example I A copolymer comprised of 75 percent p-tertiary butylstyrene and 25 percent isoprene was prepared as follows:

Into a 2 liter stirred reaction flask in a thermostatically controlled water bath held at 30 C. was added 800 grams of deionized water, 20 grams of a cationic dispersant, Siposan 7LUF (55% active), an alkyl dimethyl benzyl ammonium chloride manufactured by Alcolac Chemical Corporation. The pH of the reaction mixture was adjusted to 3.5 with acetic acid and the mixture was stirred with a N purge for 30 minutes whereupon 30 grams of tertiarybutylstyrene, 10 grams distilled isoprene and 0.5 gram cumene hydroperoxide (70% active) was added to the reaction flask. To the reaction flask was then added the following reactants which were continuously pumped into the flask in separate streams:

Amount of Rate of reactants addition S tree omposition of stream N 0. (grams) to flask (grams/hr.)

1 Formaldehyde sodium su1f0xylate 4. 0 10 Deionized water 306 2 'Iertiary-butyl styrene. 450 30 Isoprene (distilled) 150 Cumene hydroperoxide (70% active) 5 1 3 Siposan 7 LUF (55% active) 40 13 Deionized water (pH adjusted to 3.5 360 with acetic acid) eating solutions containing varying amounts of the copolymer ranging from 0.1 percent to 1 percent by weight.

Strips, 6" x 11" were cut from unbleached waterleaf kraft paper, weighed and then dipped in the copolymer dispersions for 2 minutes. Upon removal, the strip was blotted to remove excess treating material and then cured on a hot plate for 4 minutes at 120 C. After curing the strips were reweighed to determine the amount of copolymer deposited on the surface of the paper strip.

The treated papers were then evaluated for water repellency, dry tensile strength and fold endurance.

Water repellency was determined using a KBB size tester manufactured by Testing Machines, Inc.

The instrument measures the time (in seconds) required to establish a flow of a given quantity microamps) of electricity through a paper specimen placed between a lower zinc electrode and an upper, water soaked porous bronze electrode. The longer the time interval the greater the water repellency of the specimen.

Dry tensile tests were run on 0.5 x 7 inch strips of paper according to a test described under TAPPI (Technical Association for the Pulp and Paper Industry) designation T404-05-61.

Fold endurance Was determined according to a test known as the MIT Folding Endurance test and is described under TAPPI designation T423 m-SO. Folding endurance is a measure of the strength of the treated paper and is recorded as the total number of double folds required to sever the paper at the crease when a uniform folding rate (175 double folds per minute) is used, and the strip is under a tension of 1.5 kg.

The water repellency, dry tensile strength and fold endurance of the treated papers are recorded in Table I below.

The water repellency, dry tensile strength and fold endurance of unbleached waterleaf kraft paper treated in the above manner with aqueous dispersions of emulsion polymerized copolymers prepared by reacting p-tertiary butylstyrene and isoprene at monomer ratios of 87.5/ 12.5 and 50/50 respectively following the polymerization procedure described above are also recorded in Table I below.

For purposes of contrast, the water repellency, dry tensile strength and fold endurance of untreated unbleached waterleaf kraft paper (sample number 24) as well as the kraft paper treated with varying concentrations of p-tertiary butylstyrene homopolymer following the above treating procedure (sample numbers 18 to 23) are also recorded in Table I below.

Only sample numbers 1 through 17 are examples of this invention; other samples are for purpose of compari son and contrast.

TABLE I Composition of co olymer Amount 1 of (percent by we ght) copolymer KBB size Dry tensile MIT told Sample No. deposited on (sec.) (lbs/0.5 x 7' (1.5 kg. wt.)

p-Tert. Isoprene paper surface strip) butylstyrene (percent) 87. 5 12. 5 27 7. 8 16. 96 198 87. 5 12. 5 78 56. 2 16.32 208 87. 5 12. 5 1.41 87.3 16.19 216 87. 5 12. 5 1. 52 90. 1 16. 46 240 87.5 12.5 1. 95. 5 17. 22 177 87. 5 12. 5 2. 34 103. 9 16. 98 190 75. 0 25.0 .21 112. 1 16.94 217 75.0 25.0 73 111. 2 17. 83 143 75. 0 25. 0 1. 49 126. 5 17. 91 151 75.0 25.0 1. 79 120. 0 18. 20 139 75. 0 25. 0 2. 08 137. 8 17. 22 166 75. 0 25. 0 2. 59 141. 6 18. 04 209 50. 0 50. 0 27 77. 4 17. 50 150 50. 0 50. 0 82 98. 9 18. 12 172 50. 0 50. 0 1. 46 118. 4 17. 51 50. 0 50. 0 1. 80 119. 1 17. 86 175 50. 0 50. 0 2. 09 139. 6 17. 76 216 100. 0 0. 0 33 0. 4 16. 58 186 100. 0 0. 0 76 2. 1 16. 12 103 100. 0 0. 0 1. 51 5. 6 16. 75 158 100. 0 0. 0 1. 85 14. 4 17. 52 149 100. 0 0. 0 1. 96 21. 3 16. 42 136 100. 0 0. 0 2. 55 54. 4 17. 52 172 Control (no treatment) 0. 00 0.3 16.75

1 Based on dry weight of pulp.

By referring to Table I it is at once apparent that paper sheet treated with the p-tertiary-butylstyrene copolymer (sample numbers 1 through 17) showed a substantial increase in water repellency over paper sheet treated with compared to the homopolymer treatment or the control sample (sample number M).

Example III equivalent amounts of the p-tertiary-butylstyrene homo- 5 Unbleached hardwood sod-a pulp was beaten to a Canapolymer and without any diminution in dry tensile dian Standard Freeness of 390 milliliters, and a 5 gram strength or fold endurance when compared to the homoaliquot of the pulp was used to prepare a handsheet from polymer treatment or the control sample. the pulp. The pulp slurry was diluted to about 0.5 percent Example H consistency and 1. 0 percent of a 50 percent p-tertiary- 10 butylstyrene/SO percent isoprene copolymer based on the e effectiveness of t py butylstyrpne/lsoprene dry fiber weight of the pulp was added to the pulp slurry p y h descflhed 1h h p I as addltlves to Paper as a 1.0 percent solids dispersion. To the pulp slurry was p p to Improve the Water reslstanqe of Products p p added 3 percent alum based on the dry fiber. A handsheet therefrom Was determmeq accorqlng t0 3 Standard was made from the pulp slurry on a Williams handsheet oratory procedure Accordmg to thls a yp p e 15 machine at 70.3 gm./m. basis weight. The wet handsheet unbleached hardwood P p treated Wlth Sulfuric acld W was dried in an Elmes laboratory hot press at 115 C. for formed into a well beaten aqueous Suspension (Cahadlah 4 minutes. The dried papers were conditioned for 48 hours Standard freeness 015400 and 2 P5113?nt 0f alhhl based at 73 F. and 50 percent R.H. The handsheet when tested on thehhel's thfilelh was addhd to the dlhltued to in the KBB size machine required 201.9 seconds to estabapproximately 0.4 percent consistency to provide optimum lj h a fl w of 80 microamps through the paper. sulfate 101'1 concentration; the pH of the slurry was 4 2. By way f contrast, a handsheet prepared in a manner 9 ep p g of t e slurry was then added, identical to the above with the exception that the pulp Stlfflflg, aqueous dlspefslohs dlhlted to 1 h sohds slurry was treated with 1 percent of a 50 styrene/50 iso- COIIQBINIatIOII 0f P Y Q formed from val'ylhg P prene copolymer required 112.9 seconds to establish a portions of comonomers 1n the concentrations shown m fl f 80 microamps through the paper.

Table II below. Handsheets were prepared (accord1ng In a similar manner other fibrous materials such as a mqdlficatwn of TAPPI Stahdard cotton textiles, synthetic fibers or leather are treated with Wllhams handsheet machlhe 7 ghh/m'z 'hasls equivalent amounts of copolymers formed from the other U- h Sheet h then drled 111 Hydrolafre tertiary alkylstyrenes and conjugated aliphatic diolefins Oratory Press for 4 mlhhthsa the 'P platen of was mentioned above so as to improve the water repellency of heated to 120 C. The dried sheets were conditioned for the fib materiaL 48 hours at 73 F. and 50 percent relative humidity and What is claimed tested for water resistance, dry tensile strength and fold A fib material f improved water repellency endurance according to the testing procedures described having a copolymer f a tertiary alkylstyrene having the Example structural formula For purposes of contrast the water repellency, dry tensile strength and fold endurance of paper sheets prepared CH=CH from unbleached hardwood pulp to which no polymeric additive had been incorporated (sample number M) as well as paper sheets prepared from unbleached hardwood 40 pulp to which varying concentrations of p-tertiary butylstyrene homopolymer had been added (sample numbers R J to L) following the procedures are also recorded in Table II below. Only sample numbers A through I are wherein R is a tertiary alkyl group containing 4 to 20 carexamples of this invention. bon atoms and a conjugated aliphatic diolefin distributed TABLE 11 Amount 1 of Composition of copolymer copolymer KBB size Dry tensile MIT fold Sample No. incorporated (see) (lbs./0.5'x7' (1 kg. wt.) p-Tert. Isoprene in pulp strip) butylstyrene (percent) 87.5 12.5 0.10 4.9 9. 24 s 87. 5 12. 5 0. 25 53. 7 9. 12 10 87.5 12.5 0.50 68.5 9. 49 7 75.0 25.0 0.10 0.3 9.26 9 75. 0 25. 0 0. 25 64. 1 9. a3 14 75.0 25.0 0.50 79.1 9.23 9 50.0 50.0 0.10 4.8 9.50 11 50. 0 50. 0 0. 25 62. 3 9. a5 11 50. 0 50. 0 0. 50 85. 2 9. 51 9 100.0 0.0 0.10 2.0 9.14 9 100. 0 0. o 0. 25 1. 9 9. as 10 100.0 0.0 0.50 1.3 8.96 7 Control (no treatment) 0. 00 0. 4 8. 98 10 1 Based on dry weight of pulp.

By referring to Table II, it is at once apparent that substantially uniformly throughout the fibrous material, paper sheets prepared from pulp slurries treated with the said copolymer being formed from between about 10 to p-tertiary butylstyrene copolymer (sample numbers A about 90 percent by weight of the tertiary alkylstyrene and through I) showed a substantial increase in water repelabout 10 to about 90 percent by weight of the conjugated lency over paper sheets prepared from pulp slurries treated diene, said copolymer being present in the amount of with equivalent amounts of the p-tertiary-butylstyrene from about 0.05 to about 25 percent based on the weight homopolymer (sample numbers LL) and without any of the fibrous material. diminution in dry tensile strength or fold endurance when 2. A paper article of improved water repellency having a copolymer of a tertiary alkylstyrene having the structural formula CH=CH wherein R is a tertiary alkyl group containing 4 to 20 carbon atoms and a conjugated aliphatic diolefin distributed uniformly throughout the paper, said copolymer being formed from between about 25 to about 85 percent by weight of the tertiary butylstyrene and about 15 to about 75 percent by weight of the conjugated diene, said copolymer being present in the amount of from about 0.1 to about 3.0 percent based on the weight of the paper.

3. The paper article of claim 2 wherein the tertiary alkylstyrene is p-tertiary butylstyrene.

4. The paper article of claim 2 wherein the conjugated aliphatic diolefin is isoprene.

References Cited UNITED STATES PATENTS OTHER REFERENCES Marvel, C. S. et al., Copolymers of Butadiene With Alkyl, Aryl, Alkoxyl, and Phenoxyl Styrenes, Ind. Eng. Chem., vol. 40, No. 12 (1948), pp. 2371-3, TS IA58.

WILLIAM D. MARTIN, Primary Examiner.

20 M. LUSIGNAN, Assistant Examiner. 

